Tire rubber compositions have been previously developed that are capable of roughening of the tread surface and improving affinity with ice with the object of improvement of friction of a studless tire on ice.
For example, Patent Document 1 contains mention of a tire tread rubber composition composed of, relative to 100 parts by mass of a rubber component composed of diene type rubber, greater than or equal to 10 parts by mass and less than or equal to 50 parts per weight of a polymer gel (i.e. cross-linked rubber particles of 40 to 200 nm average particle diameter), and greater than or equal to 20 parts by mass and less than or equal to 40 parts by mass of a powder of 10 to 500 .mu.m average particle diameter composed of a plant porous carbide ([Claim 1]). Moreover, in addition to blending a large amount of the powder composed of the plant porous carbide, the polymer gel (i.e. the cross-linked rubber particles) is used. Thus while realizing the maximum moisture absorption effect due to the porous carbide powder, it is possible to sufficiently maintain road contact surface area, and knowledge is mentioned of the obtaining of a motion performance improvement effect at low temperature, i.e. performance on ice and performance on snow.